Add a hot water recirculation system that keeps warm water moving in the pipes. A dedicated return line gives the best result at every fixture. A crossover valve under the farthest sink is the retrofit option, and it serves that fixture. A timer or demand control limits the energy the pump uses.
Why does hot water take so long to arrive?
The water sitting in the pipe between the heater and the faucet cools off when nobody is using it. When you open the tap, that cooled water has to be pushed out before hot water reaches you. The longer the run and the larger the pipe, the longer the wait, which is why the fixture farthest from the heater is usually the slowest.
Two things you can do first are cheap. The Department of Energy says to insulate hot and cold water pipes in unconditioned spaces such as garages, attics and crawlspaces, and for at least six feet from the tank. Our page on whether to insulate your hot water pipes covers what insulation does and does not fix. Insulation slows the cooling, but it does not remove the wait.
What are your options for faster hot water?
| Option | How it works | Reaches every fixture? | What it needs |
|---|---|---|---|
| Dedicated return line and pump | A separate pipe carries cooled hot water back to the heater | Yes, if the loop passes near the fixtures | A return line in the walls, a pump and a control |
| Crossover (bypass) valve | A valve under the farthest sink connects hot and cold, and the cold line serves as the return | No, it serves the loop it sits on | A valve and a pump at the heater, no new pipe |
| Timer only | Runs the pump at set times | Depends on the system | A timer |
| Demand control | Runs the pump when someone presses a button or a sensor detects use | Depends on the system | A switch, sensor or flow detector |
| Tankless with built-in recirculation | The heater manages a recirculation loop itself | Depends on the plumbing | Compatible unit and piping |
A smart faucet can't make hot water arrive sooner, since it waits on the same hot water line; see what a smart faucet is.
### Dedicated return line
Taco's SmartPlus-e instructions say it is designed to increase hot water comfort while conserving water and energy, and that by recirculating cooled hot water back to the water heater the wait is reduced to seconds. The sheet requires a dedicated hot water recirculation line in the piping system. Taco says its circulator suits most homes with supply lines up to 300 feet. This is the design that fits new construction and remodels where the walls are open, since the return pipe has to be run.
### Crossover valve
For homes with no return line, a valve under the farthest sink can create a loop using the cold line. Taco's Hot-Link instructions describe a valve that creates a return loop through the cold line from the furthest fixture back to the water heater. An internal thermal sensor disc closes when hot water reaches the valve, and an internal flow check prevents cold water from backing into the hot line. Taco says the average family can achieve yearly savings of up to 12,000 gallons of water normally wasted down the drain while waiting for hot water, and that the circulator suits most homes with hot supply lines up to 150 feet. That figure is Taco's estimate and depends on the home.
Grundfos's Comfort System uses the same approach with a thermal bypass valve under the sink. Grundfos warns that it is not an anti-scald device, and that after installation you may find some warm water in the cold water line at the sink where the valve is installed. It says the warm water dissipates in a very short time once the cold line is opened. Our page on whether a recirculating pump heats your cold water lines covers what that means in practice.
The limit is in the design. The valve serves the run it sits on, and Taco says that a home with more than one run may need another valve at the end of each run. So a crossover system speeds up the fixtures it covers, not automatically every faucet in the house.
### Tankless with a built-in loop
Some tankless heaters manage the loop themselves. Navien's manual says the recirculation feature on its "A" models eliminates any minimum flow requirement and any hot, cold, hot stacking, and gets hot water to fixtures more quickly. It also warns that energy consumption increases because the heater works to keep the loop at temperature, and it points to Intelligent Preheating, a timer or the HotButton kit to limit that. If you have a tankless unit that goes cold mid-shower, see why a tankless heater goes cold mid-shower.
What does recirculation cost in energy?
Continuous recirculation is the costly setting. The Department of Energy's Building America strategy guideline says recirculating systems generally have much higher distribution losses than non-recirculating ones, although they reduce hot water waiting time and water waste. It describes four ways to control the pump: continuous, temperature modulation, a timer and demand controls. In a monitored study it cites, demand controls reduced heat loss more than the timer and temperature modulation strategies.
Practical controls look like this:
- Timer. Grundfos suggests setting the pump to run around peak use, from about 30 minutes before the first shower until 15 minutes after the last shower. It notes each programming tab on its timer equals 15 minutes.
- Demand control. The DOE says demand controls switch the pump on when hot water is requested, by a button, a motion sensor or a flow meter at the start of the loop.
- Navien's own options. On its tankless units with built-in recirculation, Navien points to Intelligent Preheating, a timer or the HotButton kit to limit the added energy use.
- Learning control. Taco's SmartPlug records daily hot water use during the week and runs the pump at the same times the following week, and it adjusts if your pattern changes.
Whether it pays for itself depends on your home, and our page on whether a hot water recirculation pump is worth it walks through the trade-offs.
What can go wrong?
Two failures show up often. If hot water only arrives while the pump runs, a check valve or bypass valve is usually the cause, and we cover that on why there is no hot water unless the recirculation pump is running. If only one shower runs cold, see why one shower has no hot water.
A system that never gets hot water to a far bathroom may also be a sign the water heater is undersized or has a problem of its own, and why you might have no hot water covers the common ones. If it is scalding at some taps, Grundfos's warning that the bypass valve is not an anti-scald device is worth remembering, so set the water heater with care.
Grundfos sells both kinds of pump. See whether a Grundfos recirculation pump needs a return line, Grundfos COMFORT pump control modes and how long the Comfort System warranty lasts.
What should you ask a plumber?
Bring up the layout of your house. Ask whether a return line exists, how far the farthest fixture is from the heater, whether you have one run or several, and whether your heater is a tank or tankless model. The answers decide whether a crossover valve is enough or whether a return line is worth the wall work. A plumber can also size the pump, set the timer and check the flow direction and check valves so the system works the first time.
HQ Plumbing and Air is licensed and insured, takes emergency calls 24/7, and gives free estimates with an upfront price before work starts. See our water heater services.
Navien's manual says its heater will not deliver hot water instantly unless a recirculation line has been installed. Our page on why a Navien tankless gives cold or no hot water covers that setting. For a restaurant, the county sets a limit on the wait; see the 45 second hot water rule.